Organization of parameters

I'd like to document the discussion on how to organize the parameters here.

The current structure is as follows: There are a number of "default" namelists:

• VAR_Lattice
• VAR_Model_Generic
• VAR_QMC
• VAR_QMC
• VAR_TEMP
• VAR_Max_Stoch

where VAR_Lattice and VAR_Model_Generic are supposed to be used in every hamiltonian. On top of that are a number of model specific namelists e.g. VAR_Hubbard.